JVET-L0280 CE3-related: Intra mode coding [L. Zhao, X. Zhao, X. Li, S. Liu (Tencent)]
In this contribution, it is proposed to signal 6 MPMs and only 32 remaining modes for each coding unit. To code an intra prediction mode, an MPM flag is firstly signaled. If the MPM flag is true, then truncated unary codeword with bypass coding is used to signal the MPM index. Otherwise, 5-bit fixed length coding is used to signal the remaining mode. Simulation results reportedly show that, with almost no impact on run-time, average -0.49% and -0.16% BD-rate change is achieved on top of VTM2.0.1 for all intra (AI) and random access (RA) configuration under common test condition.
The 32 remaining modes are determined from the MPMs.
The MPM derivation is same as in JEM
More analysis was required to assess the complexity of the selection process of 32 remaining modes.
It was also asked if this causes visual artefacts
The gain compared to 6 MPM with full set of modes is probably lower.
Further study in a CE was planned (with the adopted version of 6 MPM).